After a marathon session of debates and amendments on Friday, city aldermen approved a bill banning smoking in most bars and restaurants.

The bill, approved 20-7, would ban indoor smoking — with several key exceptions — contingent on St. Louis County voters approving a similar ban on the Nov. 3 ballot.

That vote, in effect, will decide the smoking ban issue for much of the region.

The plan passed at City Hall, like the county version, exempts casino floors, some hotel rooms, private clubs and tobacco stores.

But, in the city, small bars — defined as establishments with 2,000 square feet or less of service space where food sales are “incidental” to alcohol consumption — would be allowed to wait five years before having to comply with the ban.

The provision was introduced to protect neighborhood taverns already struggling in a tough economic climate. The county plan has a provision exempting “drinking establishments” — where food makes up 25 percent or less of total sales — from the ban altogether.

For most city businesses, the ban would go into effect Jan. 1, 2011.

Supporters of the city’s ban, such as the mayor and others, were concerned that acting alone would put St. Louis businesses at risk of losing customers across the city limit.

It was also the proposal that backers thought had the best chance of passing, even if some criticized it as toothless.

“It’s just not pure enough to win the support of many groups,” sponsor Alderman Lyda Krewson said. “But I consider this to be a pragmatic bill. This bill is not a bill for the extremists on either side.”

The local chapter of the American Cancer Society issued a statement immediately after the decision saying they were “extremely disappointed” by the “watered down smoke free law.”

“Partial measures work for politicians but not for health,” the statement said. “In essence, we’re telling some workers they warrant legislative protection, while telling others they don’t.”

Before sending it to the mayor’s desk for final approval, aldermen must vote one more time on the proposal. It’s unlikely, though, that any aldermen — let alone enough to prevent final passage — would change their votes. Amending the bill in the latter stages is also difficult.

Aldermen opposing the bill included Benton Park Alderman Ken Ortmann, who runs a tavern in Soulard, and Bevo Mill Alderman Stephen Gregali, who at one point during the four-hour meeting asked that his ward be excluded from the ban.

This is a “chicken you know what kind of bill,” Gregali said, who protested the exemptions.

“If we’re going to ban smoking, let’s do it,” Gregali said. “If the bars aren’t going to go out of business, neither will the casinos.”

Alderman Kacie Starr Triplett introduced a measure that would have banned smoking on casino floors, but it was defeated.

“Whether it’s a small business cafe or multimillion dollar casino, no business should be exempt from ensuring that our city residents are able to breathe clean air in the workplace,” Triplett said in a statement after the vote.

St. Louis follows Kansas City, Clayton and Columbia, Mo., in passing smoke-free legislation. Illinois already has a statewide ban, meaning that, if county voters embrace a ban, most of the region would have some level of restriction on indoor smoking.

Krewson said she hopes the vote will lead to smoke-free advocates in the city to campaign in favor of the county measure.

But, Krewson acknowledged, that goes both ways.

“People that are opposed to things are often more vocal,” Krewson said.